This invention relates to switching regulators. More particularly, this invention relates to switching regulators that actively snub waveforms so that power loss is minimized and system efficiency is maintained.
Ringing waveforms and transient pulses, for example, are generally present in switching regulators, at least because of the switching action of high-power switches employed by the regulators. These ringing waveforms must be damped or they can lead to, for example, device failure, excessive electromagnetic interference (EMI) or instability.
It is generally known in the art to employ snubbers in power circuits to alter waveforms such as by damping ringing that is present in the power circuits. One well-known and often used snubber is an RC damping circuit. The RC snubber suffers because it dissipates power on all voltage excursions applied to it; thus, much power is wasted. Another known snubber is a diode RC circuit. Although the diode RC snubber provides an improvement over the RC snubber (because the diode provides better control in one direction), the diode RC snubber still suffers from severe inefficiency by dissipating power unnecessarily.
Other snubber designs are also known in the art. For example, U.S. Pat. No. 4,894,567 discloses a snubber circuit that includes a semiconductor switching element, a capacitor and a shunting inductance. And U.S. Pat. No. 5,414,613 discloses a snubber circuit that includes a semiconductor switching element, a pair of diodes, an inductor and a capacitor.
These snubber designs also pose inefficiency problems. This is especially the case when the designs are applied to circuits involving only a few watts of power. Furthermore, they employ additional circuit components that introduce significantly increased cost and circuit complexity.
What is desired, therefore, is to provide a method and apparatus for actively altering waveforms in switching regulators so that any loss of power or efficiency is minimized and so that cost and circuit complexity can be minimized.